Minimally invasive medicine, the practice of gaining access into a blood vessel, duct, or organ using a wire guide to facilitate the subsequent introduction or placement of catheters and other medical devices, has been evolving since the Seldinger technique was first popularized during the late 1950s and 1960s. A significant advance was gaining the ability to exchange medical devices over a single indwelling wire guide without requiring displacement of the wire in the process and loss of access to the site. This ‘over the wire’ (OTW) exchange technique requires an extra long guide wire so that control over the wire could be maintained at all times during the procedure. To accomplish this, the portion of the wire extending out of the patient must be at least as long as the device itself so that a proximal portion of the wire could be secured at all times maintain longitudinal positioning, typically by an assistant standing well behind the physician. For example, endoscopic catheters that are used to access the biliary system are typically 200 cm or more in length, requiring a wire guide of more than 400 cm (e.g., 480 cm) to be long enough to remain in the duct during the exchange. To remove the catheter over the wire, the physician and an assistant must carefully make a series of well-coordinated, one to one movements between the exchange wire and device. The assistant pushes the wire the same amount as the physician pulls back on the catheter until the device is completely outside of the patient and the physician gains control over the wire at the port of the scope. The assistant then pulls the device off of the wire such that a second device can be fed back over the wire and into the patient to perform a second operation, requiring the same push-pull technique in reverse. This procedure requires a well-trained assistant, who actually is responsible for the advancement of the wire, instead of the physician. In biliary ERCP, this lack of wire guide control can be a disadvantage when cannulating the ampullary orifice because the techniques used are typically highly dependent on good verbal communication between the physician and assistant, and the experience of the latter.
Although the ‘long wire’ or OTW technique still remains a commonly used method of exchanging devices in the biliary system, a technique was developed which allowed for a much shorter wire guide and more physician control over the wire. Variously known as the ‘rapid exchange,’ ‘monorail,’ or ‘short-wire’ technique, it differs from the OTW technique in that instead of the device being introduced over the length of the wire guide, the wire guide is coupled for only a portion of the length of the catheter device. The device is fed over the wire guide, which then exits the passageway or a coupling portion of the catheter at a point between the catheter's distal end and the proximal portion via a port or channel formed in the side of the catheter, typically located within the distal portion of the device. This allows the physician to have control of the proximal or external portion of the wire at all times as it exits the patient or scope and reduces the need for coordinating device movements with an assistant. When the coupled portion exits the patient (or endoscope in the case of gastroenterological or other endoscopic procedures), the physician performs a short exchange (instead of the traditional long-wire exchange, which in biliary procedures, requires the assistant to stand well out of the sterile field in order to assist with the exchange). With certain other devices, the catheter is split or torn away to uncouple it from the wire as the catheter exits the patient. To introduce the device, the coupled portion of the catheter is advanced over the proximal end of the wire guide, while the physician is careful to maintain the wire in position so that its distal end is maintained within the work site and access is not lost.
Rapid exchange or short wire techniques have proven particularly desirable in coronary and vascular medicine whereby it is common for a sequence of procedures using multiple catheter-based devices to be performed over a single wire, such as stent placement following angioplasty. Another example of where short wire exchange techniques are often used is in endoscopic procedures performed in the pacreatobiliary system. Typically, an ERCP (endoscopic retrograde cholangiopancreatography) procedure is performed by introducing a catheter device from a duodenoscope through the ampullary orifice (Papilla of Vater) and into the biliary tree, which includes the bile duct, pancreatic duct, and hepatic ducts of the liver. The cannulation device, which typically comprises a sphincterotome/papillotome or ECRP catheter, is introduced into the biliary tree to perform a first operation, which could be diagnostic in nature, such as injecting contrast media, or for therapeutic purposes, such as enlarging the ampullary orifice. When a second medical operation is required, such as to remove a stone, open a stricture, sample tissue, etc., a second or peripheral device, e.g., balloon, basket, snare, biopsy brush, dilator, stent delivery catheter, etc., can be introduced over the original wire guide to perform a secondary therapeutic procedure.
While OTW techniques have permitted the exchange of devices, the development of short wire techniques has found acceptance by physicians who prefer to maintain greater control of the wire guide at the scope. Well-known examples of this rapid exchange technology are the devices comprising the MICROVASIVE RX BILIARY SYSTEM™ (Boston Scientific Corporation, Natwick, Mass.) in which the catheter portion of the devices include an internal lumen extending between a distal opening and a proximal side opening spaced 5-30 cm therefrom, depending on the device, thereby requiring an exchange of that length as the device is being removed over the 260 cm JAGWIRE® Guidewire guide developed for that system. An example of a sphincterotome of this system (AUTOTOME™ Cannulating Sphincterotome) is depicted in FIG. 1. Extending proximally from the proximal side opening, the lumen forms a ‘C-channel’ (shown in FIG. 2) that holds the wire guide within the catheter as the catheter portion is introduced into the scope, but allows the wire to be laterally pulled out of the channel to gain access of the wire at the biopsy port of the scope as the catheter is being removed from the scope (FIG. 3), so that a second catheter type device (e.g., balloon, basket, stent delivery catheter, etc.) can be subsequently fed over the proximal end of the wire. As the distal portion of the first device is exiting the scope, a short exchange is required (coordinated push-pull movements between the physician and assistant) that is similar in practice to that used in an OTW procedure, until the physician gains control of the wire and the assistant can pull off the first device without risking loss of access. The proximal end of the wire guide is typically secured to the scope during much of the procedure to prevent loss of access, but it must be disengaged from the scope to allow the exchange and removal of the catheter.
While the Microvasive system has offered modest time savings, more physician control of the wire, and placed less reliance on the skill of the assistant to help perform the exchange, a short exchange procedure is still required in which care must be taken to prevent loss of wire guide access to the duct, particularly since the wire guide cannot be secured to the scope during removal of the catheter. Because the wire guide resides in the channel of the catheter and the coupled devices are constrained together in the accessory channel, uncoupling must take place as the distal portion of the catheter exits the proximal end of the scope. The process is further slowed by the frictional resistance between the wire and catheter, which remains a problem in subsequent exchanges as devices are fed or removed over the wire residing in the catheter lumen or C-channel.
Having a C-channel extending along the catheter can result in certain clinical disadvantages. For example, the split in the catheter provides an entry point for blood and bile, a known source of viruses and bacteria, to enter the catheter lumen and migrate to the proximal end of the device where they typically leak out onto the floor and clothing of those involved in the procedure. The channel also represents a point of potential air leakage, which can compromise the ability to maintain adequate insufflation within the duodenum during the procedure. Another disadvantage of a C-channel is that it degrades the integrity of the catheter, which can be problematic in a cannulating device (such as a deflecting Sphincterotome) when attempting to push through or ‘lift’ the papilla to straighten the entry pathway into the duct, or when pushing through a stricture.
The current rapid exchange or short wire system also fails to address some of the shortcomings found in the traditional OTW method. For example, recannulation of the papilla is required when placing multiple plastic drainage stents side by side since the delivery system must be removed to disconnect the wire. Furthermore, existing devices do not offer the ability to place a second wire guide after the first one, such as to place stents in multiple ducts, since the catheter, which could otherwise serve as a conduit, must be removed from the patient and work site before it would have a free lumen for a second wire. Another disadvantage of current systems for exchanging biliary devices is the incompatibility between the two systems. Long wire devices lack the side access port for use with a short exchange wire and the MICROVASIVE RX BILIARY SYSTEM™ devices with C-channels are poorly configured for long wire exchange since once the C-channel has been breached during the first exchange, it is difficult to introduce a long wire through the proximal wire guide access port (which includes the open channel) and keep it from slipping from the channel as it is being introduced. Further, the C-channel is typically not compatible with smaller-diameter wire guides (less than 0.035″) for the same reason. Incompatibility between systems means that physicians cannot take advantage of all of the choices available when selecting the best device and treatment for a particular patient.
What is needed is an improved short-wire system and technique for efficiently and reliably exchanging devices within a work site which is compatible with long wire exchange method and which addresses the other deficiencies described above.